1. Field of the Invention
The present invention relates to electron beam technology. More particularly, the present invention relates to an apparatus including a microcolumn and a scanning probe microscope for surface inspection and microfabrication.
2. Description of the Related Art
The recent trend in electron beam technology is toward low voltage scanning electron microscopy. Low voltage scanning electron microscopy has applications in surface inspection, metrology, testing and lithography.
Conventional scanning electron microscopes (SEMs) are large immobile devices. Although SEMs have many applications, such as semiconductor-related inspection and testing, conventional SEMs are limited in their usefulness because of their size, immobility and associated costs. For instance, because the sample being observed, as opposed to the SEM, must be moved during the inspection process, a conventional SEM requires the use of a vacuum chamber that is much larger than the sample. Further, the sample must be positioned at an angle relative to a conventional SEM to produce a beam incidence angle required for three-dimensional-like surface feature imaging. This makes handling of large or delicate samples difficult. Moreover, throughput of a conventional SEM is limited because only one microscope can observe a sample at a time.
An effort to improve SEMs has resulted in miniature electron beam microcolumns (xe2x80x9cmicrocolumnsxe2x80x9d). Microcolumns are based on microfabricated electron optical components and field emission sources operating under the scanning tunneling microscope (STM) feedback principle. Microcolumns are discussed in general in T. H. P. Chang et al., xe2x80x9cElectron Beam Technologyxe2x80x94SEM to Microcolumn,xe2x80x9d 32 Microelectronic Engineerng 113-30 (1996) and T. H. P. Chang et al., xe2x80x9cElectron-Beam Microcolumns for Lithography and Related Applications,xe2x80x9d B 14(6) Journal of Vacuum Science Technology 3774-81 (November/December 1996), which are incorporated herein by reference.
Although microcolumns provide high resolution at a high scanning speeds, they are unable to provide atomic resolution. Information at the atomic level, such as spectroscopy or topography, may be necessary for in-line quality control or registration in microfabrication. In addition, for lithography, microcolumns are limited in their ability to write very small features. Thus, it would be advantageous to provide an apparatus having a wider range of resolution than that of a microcolumn and capable of writing atomic-scale features.
The present invention addresses these problems by combining a microcolumn and a scanning probe microscope in a single apparatus. The apparatus provides a greater range of resolution and scan area size than either the microcolumn or scanning probe microscope alone. In addition, the small size of the apparatus makes it suitable for use in confined spaces. This versatile apparatus has applications in the areas of imaging, lithography and spectroscopy.
In accordance with one aspect of the invention, an apparatus for surface inspection or microfabrication of a wafer includes a microcolumn and an associated scanning probe microscope. Both may be mounted on a single support structure. The scanning probe microscope, which, for example, can be a scanning tunneling microscope or an atomic force microscope, provides atomic resolution of features on the wafer, while the microcolumn allows coarse rapid scanning of the overall sample.
In accordance with another aspect of the invention, an apparatus for surface inspection or microfabrication of a wafer includes an array of microcolumns and at least one scanning probe microscope. The at least one scanning probe microscope is associated with at least one microcolumn in the array of microcolumns to provide atomic resolution of features on the wafer.
In accordance with still another aspect of the present invention, a method for inspecting or patterning a wafer includes providing an array that includes multiple microcolumns and at least one scanning probe microscope and placing the array above the wafer such that each microcolumn of the array of microcolumns is situated above a respective die of the wafer. The method further includes inspecting or patterning the dice of the wafer or selectively exposing patterns on the dice with the microcolumns. The scanning probe microscope precisely positions the array above the wafer and/or patterns and inspects atomic-scale features on the dice. The simultaneous operation provides a fast inspection or lithography process.